Apache Module mod_md

Available Languages: en

+ + + + +

Description:	Managing domains across virtual hosts, certificate provisioning + via the ACME protocol +
Status:	Extension
Module Identifier:	md_module
Source File:	mod_md.c
Compatibility:	Available in version 2.4.30 and later

Summary

+ +

+ This module manages common properties of domains for one or more virtual hosts. + Specifically it can use the ACME protocol + (RFC Draft) + to automate certificate provisioning. These will be configured for managed domains and + their virtual hosts automatically. This includes renewal of certificates before they + expire. The most famous Certificate Authority currently implementing the ACME protocol + is Let's Encrypt.

+ +

Warning

This module is experimental. Its behaviors, directives, and + defaults are subject to more change from release to + release relative to other standard modules. Users are encouraged to + consult the "CHANGES" file for potential updates.

+ +

Simple configuration example:

+ +

TLS in a VirtualHost context

MDomain example.org
+
+<VirtualHost *:443>
+    ServerName example.org
+    DocumentRoot htdocs/a
+
+    SSLEngine on
+    # no certificates specification
+</VirtualHost>

+ +

+ This setup will, on server start, contact + Let's Encrypt + to request a certificate for the domain. If Let's Encrypt can verify the ownership + of the domain, the module will retrieve the certificate and its chain, store it + in the local file system (see MDStoreDir) + and provide it, on next restart, to mod_ssl. +

+ This happens while the server is already running. All other hosts will continue + to work as before. While a certificate is not available, requests for the managed + domain will be answered with a '503 Service Unavailable'. +

+ +

Prerequisites

+ This module requires mod_watchdog to be loaded as well. +

+ Certificate signup and renewal with Let's Encrypt requires your server to be + reachable on port 80 (http:) from the outside. The alternative method over + port 443 (https:) is currently disabled for security reasons (status from + 2018-01-14). +

+ The module will select from the methods offered by Let's Encrypt. If LE decides + at one point in the future, to re-enable it again, mod_md will + use it when suitable. +

+ But for now, only the port 80 variant is available (termed "http-01"). Only + when LE can reach your server on port 80 will mod_md work for + you. For now, at least. +

+ If you do not want to offer any sites on port 80 any more, you may leave it open + and redirect all requests to your https: sites instead. Use the + MDRequireHttps described below to do + that in a convenient fashion. This will continue to answer http: challenges + from Let's Encrypt. +

Directives

MDBaseServer
MDCAChallenges
MDCertificateAgreement
MDCertificateAuthority
MDCertificateProtocol
MDDriveMode
MDHttpProxy
MDMember
MDMembers
MDMustStaple
MDNotifyCmd
MDomain
<MDomainSet>
MDPortMap
MDPrivateKeys
MDRenewWindow
MDRequireHttps
MDStoreDir

Bugfix checklist

MDBaseServer Directive

+ + + + + + + +

Description:	Control if base server may be managed or only virtual hosts.
Syntax:	`MDBaseServer on\|off`
Default:	`MDBaseServer off`
Context:	server config
Status:	Extension
Module:	mod_md

+ Controls if the base server, the one outside all VirtualHosts should be managed by + mod_md or not. Default is to not do this, for the very reason that + it may have confusing side-effects. It is recommended that you have virtual hosts + for all managed domains and do not rely on the global, fallback server configuration. +

+ +

MDCAChallenges Directive

+ + + + + + + +

Description:	Type of ACME challenge used to prove domain ownership.
Syntax:	`MDCAChallenges name [ name ... ]`
Default:	`MDCAChallenges tls-sni-01 http-01`
Context:	server config
Status:	Extension
Module:	mod_md

+ Sets challenge types and their execution order when proving domain ownership. + The names are protocol specific. + The current ACME protocol version implemented by Let's Encrypt defines two challenge + types that are supported by mod_md. By default, it will try + the one on port 443 when available. +

+ +

MDCertificateAgreement Directive

+ + + + + + +

Description:	The URL of the Terms-of-Service document, that the CA server requires you to accept.
Syntax:	`MDCertificateAgreement url-of-terms-of-service`
Context:	server config
Status:	Extension
Module:	mod_md

When you use mod_md to obtain a certificate, you become a customer of the CA (e.g. Let's Encrypt). That means you need to read and agree to their Terms of Service, + so that you understand what they offer and what they might exclude or require from you. + mod_md cannot, by itself, agree to such a thing. +

In case of Let's Encrypt, their current Terms of Service are here. + Those terms might (and probably will) change over time. So, the certificate renewal might require you to update this agreement URL.

Example

MDCertificateAgreement https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf
+MDomain example.org www.example.org mail.example.org

+ +

MDCertificateAuthority Directive

+ + + + + + + +

Description:	The URL of the ACME Certificate Authority service.
Syntax:	`MDCertificateAuthority url`
Default:	`MDCertificateAuthority https://acme-v01.api.letsencrypt.org/directory`
Context:	server config
Status:	Extension
Module:	mod_md

+ The URL where the CA offers its service. +

+ Let's Encrypt offers, right now, two such URLs. One for the real certificates and + one for testing (their staging area, at https://acme-staging.api.letsencrypt.org/directory). + In order to have mod_md use this testing service, configure your + server like this: +

LE Staging Setup

MDCertificateAuthority https://acme-staging.api.letsencrypt.org/directory
+MDCertificateAgreement https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf

+ +

MDCertificateProtocol Directive

+ + + + + + + +

Description:	The protocol to use with the Certificate Authority.
Syntax:	`MDCertificateProtocol protocol`
Default:	`MDCertificateProtocol ACME`
Context:	server config
Status:	Extension
Module:	mod_md

Specifies the protocol to use. Currently, only ACME is supported.

+ +

MDDriveMode Directive

+ + + + + + + +

Description:	Control when it is allowed to obtain/renew certificates.
Syntax:	`MDDriveMode always\|auto\|manual`
Default:	`MDDriveMode auto`
Context:	server config
Status:	Extension
Module:	mod_md

In 'auto' mode, mod_md will drive a Managed Domain's + properties (e.g. certificate management) whenever necessary. When a MD is not used + in any virtual host, the module will do nothing. When a certificate is missing, it + will try to get one. When a certificate expires soon (see + MDRenewWindow), it will + renew it. +

+ In 'manual' mode, it is your duty to do all this. The module will provide the existing + certificate to mod_ssl, if available. But it will not contact the CA for signup/renewal. + This can be useful in clustered setups where you want just one node to perform + the driving. +

+ The third mode 'always' is like 'auto', with the difference that + mod_md will not check if the MD is actually used. +

+ +

MDHttpProxy Directive

+ + + + + + +

Description:	Define a proxy for outgoing connections.
Syntax:	`MDHttpProxy url`
Context:	server config
Status:	Extension
Module:	mod_md

Use a http proxy to connect to the MDCertificateAuthority. Define this + if your webserver can only reach the internet with a forward proxy. +

+ +

MDMember Directive

+ + + + + + +

Description:	Additional hostname for the managed domain.
Syntax:	`MDMember hostname`
Context:	server config
Status:	Extension
Module:	mod_md

+ Instead of listing all dns names on the same line, you may use + MDMember to add such names + to a managed domain. +

Example

<MDomainSet example.org>
+    MDMember www.example.org
+    MDMember mail.example.org
+</MDomainSet example.org>

+ If you use it in the global context, outside a specific MD, you can only + specify one value, 'auto' or 'manual' as the default for all other MDs. See + MDomain for a + description of these special values. +

+ +

MDMembers Directive

+ + + + + + + +

Description:	Control if the alias domain names are automatically added.
Syntax:	`MDMembers auto\|manual`
Default:	`MDMembers auto`
Context:	server config
Status:	Extension
Module:	mod_md

Defines if the ServerName and + ServerAlias values of a VirtualHost + are automatically added to the members of a Managed Domain or not. +

+ +

MDMustStaple Directive

+ + + + + + + +

Description:	Control if new certificates carry the OCSP Must Staple flag.
Syntax:	`MDMustStaple on\|off`
Default:	`MDMustStaple off`
Context:	server config
Status:	Extension
Module:	mod_md

Defines if newly requested certificate should have the OCSP Must Staple flag + set or not. If a certificate has this flag, the server is required to send a + OCSP stapling response to every client. This only works if you configure + mod_ssl to generate this (see SSLUseStapling + and friends). +

+ +

MDNotifyCmd Directive

+ + + + + + +

Description:	Run a program when Managed Domain are ready.
Syntax:	`MDNotifyCmd path`
Context:	server config
Status:	Extension
Module:	mod_md

The configured executable is run when Managed Domains have signed up or + renewed their certificates. It is given the names of the processed MDs as + arguments. It should return status code 0 to indicate that it has + run successfully. +

+ +

MDomain Directive

+ + + + + + +

Description:	Define list of domain names that belong to one group.
Syntax:	`MDomain dns-name [ other-dns-name... ] [auto\|manual]`
Context:	server config
Status:	Extension
Module:	mod_md

+ All the names in the list are managed as one Managed Domain (MD). + mod_md will request one single certificate that is valid for all these names. This + directive uses the global settings (see other MD directives below). If you + need specific settings for one MD, use + the <MDomainSet>. +

+ There are 2 additional settings that are necessary for a Managed Domain: + ServerAdmin + and MDCertificateAgreement. + The mail address of ServerAdmin + is used to register at the CA (Let's Encrypt by default). + The CA may use it to notify you about + changes in its service or status of your certificates. +

+ The second setting, MDCertificateAgreement, + is the URL of the Terms of Service of the CA. When you configure the URL, + you confirm that you have read and agree to the terms described in the linked + document. Before you do that, the CA will not hand out certificates to you. +

Example

ServerAdmin mailto:admin@example.org
+MDCertificateAgreement https://letsencrypt.org/documents/LE-SA-v1.1.1-August-1-2016.pdf
+MDomain example.org www.example.org
+
+<VirtualHost *:443>
+    ServerName example.org
+    DocumentRoot htdocs/root
+
+    SSLEngine on
+</VirtualHost>
+
+<VirtualHost *:443>
+    ServerName www.example.org
+    DocumentRoot htdocs/www
+
+    SSLEngine on
+</VirtualHost>

+ There are two special names that you may use in this directive: 'manual' + and 'auto'. This determines if a Managed Domain shall have exactly the + name list as is configured ('manual') or offer more convenience. With 'auto' + all names of a virtual host are added to a MD. Conventiently, 'auto' is also + the default. +

Example

MDomain example.org
+
+<VirtualHost *:443>
+    ServerName example.org
+    ServerAlias www.example.org
+    DocumentRoot htdocs/root
+
+    SSLEngine on
+</VirtualHost>
+
+MDomain example2.org auto
+
+<VirtualHost *:443>
+    ServerName example2.org
+    ServerAlias www.example2.org
+    ...
+</VirtualHost>

+ In this example, the domain 'www.example.org' is automatically added to + the MD 'example.org'. Similarly for 'example2.org' where 'auto' is configured + explicitly. Whenever you add more ServerAlias names to this + virtual host, they will be added as well to the Manged Domain. +

+ If you prefer to explicitly declare all the domain names, use 'manual' mode. + An error will be logged if the names do not match with the expected ones. +

+ +

<MDomainSet> Directive

+ + + + + + +

Description:	Container for directives applied to the same managed domains.
Syntax:	`<MDomainSet dns-name [ other-dns-name... ]>...</MDomainSet>`
Context:	server config
Status:	Extension
Module:	mod_md

+ This directive allows you to define a Managed Domain (MD) with specific + settings, different from the global MD* ones. For example, you can have + such an MD use another CA then Let's Encrypt, have its unique renewal duration + etc. +

Example

<MDomainSet sandbox.example.org>
+    MDCertificateAuthority   https://someotherca.com/ACME
+    MDCertificateAgreement   https://someotherca.com/terms/v_1.02.pdf
+</MDomainSet>

This is a specialized version of MDomain, + it should be used only when a fine grained configuration is required. + MDomain is the suggested choice + for the general use case.

+ +

MDPortMap Directive

+ + + + + + + +

Description:	Map external to internal ports for domain ownership verification.
Syntax:	`MDPortMap map1 [ map2 ]`
Default:	`MDPortMap 80:80 443:443`
Context:	server config
Status:	Extension
Module:	mod_md

+ The ACME protocol provides two method to verify domain ownership: one that uses + port 80 and one for port 443. If your server is not reachable by at least one + of the two, ACME will not work for you. +

+ mod_md will look at your server configuration and try to figure + out which of those are available. Then it can select the proper ACME challenge + to create a certificate for your site. +

+ However if you have some fancy port forwarding in place, your server may be + reachable from the Internet on port 443, but the local port that httpd uses is + another one. Your server might only listen on ports 5001 and 5002, but be reached + on ports 443 and 80. How should mod_md figure that one out? +

+ With MDPortMap you can tell it which 'Internet port' corresponds to which local + port. +

Example

MDPortMap 80:- 443:5002

+ This example says that the server is not reachable on port 80 from the outside, but + local port 5002 is the one responding to https: requests. +

+ +

MDPrivateKeys Directive

+ + + + + + + +

Description:	Set type and size of the private keys generated.
Syntax:	`MDPrivateKeys type [ params... ]`
Default:	`MDPrivateKeys RSA 2048`
Context:	server config
Status:	Extension
Module:	mod_md

+ Defines what kind of private keys are generated for a managed domain and with + what parameters. The only supported type right now is 'RSA' and the only parameter + it takes is the number of bits used for the key. +

+ The current (2017) recommendation is at least 2048 bits and a smaller number is + not accepted here. Higher numbers offer longer security, but are computationally more + expensive, e.g. increase the load on your server. That might or might not be an + issue for you. +

+ Other key types will be defined in the future. +

Example

MDPrivateKeys RSA 3072

+ Please note that this setting only has an effect on new keys. Any existing + private key you have remains unaffected. Also, this only affects private keys + generated for certificates. ACME account keys are unaffected by this. +

+ +

MDRenewWindow Directive

+ + + + + + + +

Description:	Control when a certificate will be renewed.
Syntax:	`MDRenewWindow duration`
Default:	`MDRenewWindow 33%`
Context:	server config
Status:	Extension
Module:	mod_md

+ If the validity of the certificate falls below duration, mod_md will get a + new signed certificate. +

+ Normally, certificates are valid for around 90 days and mod_md will renew + them the earliest 33% of their complete lifetime before they expire (so for + 90 days validity, 30 days before it expires). If you think this is not what + you need, you can specify either the exact time, as in: +

Example

# 21 days before expiry
+MDRenewWindow 21d 
+# 30 seconds (might be close)
+MDRenewWindow 30s
+# 10% of the cert lifetime
+MDRenewWindow 10%

When in auto drive mode, the module will check every 12 hours at least + what the status of the managed domains is and if it needs to do something. + On errors, for example when the CA is unreachable, it will initially retry + after some seconds. Should that continue to fail, it will back off to a + maximum interval of hourly checks. +

+ +

MDRequireHttps Directive

+ + + + + + + +

Description:	Redirects http: traffic to https: for Managed Domains.
Syntax:	`MDRequireHttps off\|temporary\|permanent`
Default:	`MDRequireHttps off`
Context:	server config
Status:	Extension
Module:	mod_md

This is a convenience directive to ease http: to https: migration of + your Managed Domains. With: +

Example

MDRequireHttps temporary

you announce that you want all traffic via http: URLs to be redirected + to the https: ones, for now. This is safe and you can remove this again at + any time. +

+ The following has consequences: if you want client to no longer use the + http: URLs, configure: +

Permanent (for at least half a year!)

MDRequireHttps permanent

This does two things: +

All request to the http: resources are redirected to the + same url with the https: scheme using the 301 + status code. This tells clients that this is intended to be forever and + the should update any links they have accordingly. +
All answers to https: requests will carry the header + Strict-Transport-Security with a life time of half a year. + This tells the browser that it never (for half a year) shall use http: + when talking to this domain name. Browsers will, after having seen this, refuse + to contact your unencrypted site. This prevents malicious middleware to + downgrade connections and listen/manipulate the traffic. Which is good. But + you cannot simply take it back again. +

You can achieve the same with mod_alias and some Redirect configuration, + basically. If you do it yourself, please make sure to exclude the paths + /.well-known/* from your redirection, otherwise mod_md might have trouble + signing on new certificates. +

If you set this globally, it applies to all managed domains. If you want + it for a specific domain only, use: +

Example

<MDomainSet xxx.yyy>
+  MDRequireHttps temporary
+</MDomainSet>

+ +

MDStoreDir Directive

+ + + + + + + +

Description:	Path on the local file system to store the Managed Domains data.
Syntax:	`MDStoreDir path`
Default:	`MDStoreDir md`
Context:	server config
Status:	Extension
Module:	mod_md

+ Defines where on the local file system the Managed Domain data is stored. This is + an absolute path or interpreted relative to the server root. The default will create + a directory 'md' in your server root. +

+ If you move this and have already data, be sure to move/copy the data first to + the new location, reconfigure and then restart the server. If you reconfigure + and restart first, the server will try to get new certificates that it thinks + are missing. +

+ +

Apache Module mod_md

Summary

Warning

TLS in a VirtualHost context

Prerequisites

Directives

Bugfix checklist

See also

MDBaseServer Directive

MDCAChallenges Directive

MDCertificateAgreement Directive

Example

MDCertificateAuthority Directive

LE Staging Setup

MDCertificateProtocol Directive

MDDriveMode Directive

MDHttpProxy Directive

MDMember Directive

Example

MDMembers Directive

MDMustStaple Directive

MDNotifyCmd Directive

MDomain Directive

Example

Example

<MDomainSet> Directive

Example

MDPortMap Directive

Example

MDPrivateKeys Directive

Example

MDRenewWindow Directive

Example

MDRequireHttps Directive

Example

Permanent (for at least half a year!)

Example

MDStoreDir Directive

Comments

Types of Configuration Section Containers